This invention, according to the statement of this description, refers to a latch mechanism for electronic locks and involves notable relevant and advantageous characteristics compared to present mechanisms that can be regarded as being of its type.
It is installed in the inner escutcheon of the lock and it is valid for doors that close on the left or on the right, and it is able to be adapted to locks whose escutcheon is very narrow such as in the case of locks for metal frames.
As it is located inside the escutcheon, this means that it can be used with a wide range of mortise locks, and advantage can even be taken of those that have already been installed, simply by changing the metal escutcheons for these electronic configuration ones.
The placement of the latch mechanism inside the inner escutcheon provides the advantages of greater security and better aesthetics.
It grants greater security because the lock is protected against being manipulated from the outside and against adverse climatic conditions.
Better aesthetics are also achieved because the outer escutcheon does not need any extraordinary dimensions for housing the latch mechanisms given that it lacks them.
Electronic locks are characterized in that they have a mechanical lock that physically secures the door to the frame and in that they have certain electronic means for authorizing the opening of that lock. The electronic means include a reader permitting the reading of data on a coded medium that can take different forms and different technologies, such as for example a magnetic card, a proximity card, a key with memory, etc. We will in general name these coded media as keys. When a key with valid data is presented, the electronic control permits the outer handle to operate one of the shafts of the mechanical lock, either by means of releasing a latch that was preventing the handle from turning or by means of activation of a clutch that connects the shaft of the handle to the shaft of the lock.
Mechanical locks can have one or several shafts. Some open the catch bolt and are usually operated by a handle or a knob. Others open or close a lever and are usually operated by means of a cylinder either with a key, or with a rotating knob. The electronic control can govern the action of one or several of the shafts depending on the applications of the lock.
In the description that follows, we refer to the shaft that controls the catch bolt of the lock and which is operated with a turn that is usually smaller than 90xc2x0 actuated by a handle or knob and forced by a spring to return to the initial rest position.
Moreover, the handle of the inner side of the door must always open the lock without the intervention of any electronic control in order to permit exit in the case of emergency. This feature is known as anti-panic.
There are numerous patents on electronic locks that describe latch mechanisms that are housed in the outer escutcheon and in which the shaft of the handle is divided into two halves. The outer half is controlled by the latch and the inner one always functions operated by the inner handle.
An improvement is to locate the latch in the inner side of the door rather than in the outside. This is a more secure solution since the system is then protected from possible manipulations. It is more reliable from the environmental point of view since the inner side usually suffers smaller variations in temperature and humidity. It can also be more aesthetic since the outer escutcheon does not have to house the latch mechanism.
Invention patent FR 2772817 describes a latch mechanism housed in the inner escutcheon and controlled by an electromagnetic vent.
The mechanism suffers from the defect of having one mounting position, in other words, it is left-handed or right-handed, and when the lock is fitted in doors of the opposite handedness, then the mechanism needs to be dismantled in order to reverse it and assemble it again, with the drawbacks for the user and risk of malfunctioning due to the handling of critical mechanisms.
The electromagnetic vent has a permanent magnet that retains the latch in its secure position. The electronic control supplies an electric current in order to cancel the magnetic field of the magnet and in this way the latch is released, pulled by a spring. Given that electromagnetic vents are efficient for retaining the armature but not for attracting it if it is a few millimeters away, the turning of the handle is used during the opening for resetting the system to its secure state. This compromises the security since if the user acts on the lock with his electronic key but fails to turn the handle, the lock remains open for an indefinite length of time.
In order to achieve the anti-panic function from the inside, the shafts of the outer or inner handles are not completely joined together but instead one drags the other after a certain rotation at no load. When the inner handle is turned these degrees of rotation at no load are exploited in order to withdraw the latch by means of a cam, in such a way that when it starts to drag the outer shaft, this shaft will already have been released. Given that the latch needs to penetrate into the piece that it locks by a minimum depth in order to be secure, the cam will have the appropriate profile for displacing the latch through that distance an angle that will preferably be as small as possible. If this angle is made too small, the profile of the cam will be very sharp and the functioning of the mechanism will not be smooth, and there will be a risk of getting blocked if the two pieces become wedged together.
Moreover, the security of the lock is based on the stresses that the latch can resist without either breaking or deforming when a torque is applied to the outer handle. These stresses are inversely proportional to the distance from the latch to the center of the axis of the mechanism. In the design described by the aforementioned patent FR 2771817 this distance has to be less than half the width of the escutcheon for the lock, which means that the narrower it is wished to make the lock, the greater are the resistance requirements for the pieces.
In general terms, the latch mechanism for electronic locks, which constitutes the object of the invention, solves the problems mentioned above, though maintaining the advantages of being housed in the inner escutcheon and of being able to be adopted to any lock.
By means of a totally different design of the latch mechanism, the following advantages are obtained:
The mechanism has no xe2x80x9chandednessxe2x80x9d so it can be fitted to left-handed and right-handed doors without any need to manipulate the mechanisms.
Once the lock has been opened, and following an interval of time, it closes again even if the handle has not been turned.
The pre-turning of the inner handle before the door is opened is made very small, though without doing away with the smoothness of the lock""s functioning and maintaining the width of the lock at minimum dimensions.
The distance from the latch to the axis of rotation can be greater than half the width of the lock, thereby reducing the stresses borne by the pieces producing the locking.
The electronic lock includes an inner escutcheon and an outer one, with square bars emerging from them and ending in the operating handles. The inner escutcheon contains the electronic control circuit and is supplied by batteries, acting on the latch mechanism itself. Moreover, the outer escutcheon is the element that supports the key reader.
The square bars act on the tumbler divided into two parts which make contact together and which we will refer to as the inner tumbler and the outer tumbler, depending on which side of the door they are fitted. Both square bars are axially connected though one can rotate with respect to the other to the degree that the tumblers do so as well; these tumblers have a relative rotary movement, though they are limited by stops in both one direction and the other. The outer tumbler is immobilized by the latch device materialized by a prismatic piece inserted in a notch or groove of that tumbler. The inner tumbler can be displaced through an angle to the degree established by the relative rotation with respect to the outer tumbler, after which both rotate together simultaneously so that the lock can open after the key reader connected electrically to the electronic control circuit accepts a key as being valid. At that moment the motor for the latch mechanism is operated in order to release the outer square bar for a few seconds in order to permit the outer handle to open the lock. This operation takes place when the door is opened from the outside. On the other hand, when the lock is operated from the inner handle, the inner tumbler rotates through the angle permitted by the free rotation mentioned earlier and during this movement the latch of the outer tumbler is mechanically released, permitting the simultaneous rotation of both tumblers to continue in order to open the lock.
The tumblers possess certain complementary lugs and windows or recesses for producing the follower action once the locking means are released.
The piece that materializes the latch is displaceable by a pair of rocker arms, which are in turn actuated by one of the two lugs provided in the lower part of the inner tumbler, with one or the other acting depending on the direction of rotation.
This latch is assisted by a spring defined by a helicoidal winding with two extensions or arms, one of which makes contact with the latch and the other is linked to an endless screw that rotates when a reducer motor is operated. Depending on the direction of rotation, the latch becomes engaged or disengaged with respect to the outer tumbler.
In order to limit the stress of rotation on the outer handle when an attempt is made to force the lock, the outermost half of the outer square bar has been provided with peripheral cuts where the square bar would break if the established limits are exceeded.
In order to facilitate an understanding of the characteristics of the invention and forming an integral part of this description, attached are some sheets of plans in whose figures the following are represented by an illustrative and non-restrictive way: